This invention relates to a grate plate arrangement for step grates. Generally, step grates include several grate plates laid out beside each other on one grate carrier to form one grate plate row; several grate plate rows laid out behind each other in the conveying direction form the step grate. The grate plate rows have a stepped arrangement, that is, the front area of each grate plate row rests on the rear area of a following grate plate row in the conveying direction. To convey granulated materials lying on the grate, in general individual grate plate rows are arranged movable in the conveying direction while other grate plate rows remain immovable.
Special problem areas of this type of step grates are the end walls of the individual grate plates. On the one hand, the end walls of the grate plates of the movable grate plate rows transport granulated materials in the conveying direction, thus subjecting them to particular wear and tear. On the other hand, the end walls of each grate plate row, together with the following grate plate row moving relative to it, form an open motion gap that prevents damaging friction, which would lead to increased wear and loss of driving power, from occurring in the overlapping area of the grate plate rows moving relative to each other. The motion gap is generally blown free by a flow of cooling air passing through it. It must be dimensioned as narrow as possible so that the proportion of cooling air emerging from the motion gap does not become uncontrolled large.
It is already known from EP 0 740 766 B1 that attaching a height-adjustable front plate to the end wall of a grate plate will allow for the precise adjustment of the motion gap. The front plates are fastened using studs which penetrate through oblong holes formed in the front plate and screwed into tapped holes formed in the grate plate. After installation, the studs are welded to the front plate and the front plate itself is welded to the grate plate. This allows the structure to bear the significant loads occurring during operation. The front plates are preferably manufactured from a heat-resistant and abrasion-resistant material.
Direct contact with the extremely abrasive material conveyed significantly wears out the bolt heads. If the front plates have to be readjusted after a longer operating period in order to readjust the motion gap increased by wear and tear, then the bolt heads have to be cut off and the shanks of the studs removed and discarded. Another disadvantage of this known arrangement lies in the fact that the studs are exposed to a high-temperature load through direct contact with the hot material, making the use of a high-temperature material necessary.